Method for manufacturing polymerized fatty acids



Dec.'29, 1953 c. G. GQEBEL 2,664,429

METHOD FOR MANUFACTURING POLYMERIZED FATTY ACIDS Fild Aug. 15, 1949'EJECTOR 17 22 FLASH VENT TILL 5 (couosusm STEAM 20 "T DR'ER. r

MONOMER V 16 p e STORAGE P A r U w a AUTOCLAVE FURNACE INVENTOR. WZW

M g ,7 Am#a- Patented Dec. 29, 1953 UNITED stares areas METHOD FORMANUFACTURING POLY- MERIZED FATTY ACIDS Charles G. 'Goebel, cincinnatiohio, assignonto Emery Industries, llnc cincinnati, Ohio, a corporationof ()hio Application August 15, 1949,:Serial No. 119,348

3 Claims. (01. 260-407) This invention relates to a method for effect- Iing the continuous polymerization of the polyunsaturated components of amixture of fatty acids, and to their separation from the monounsaturatedand saturated components thereof.

The general method of accom lishing this result involves thedimerization of the polyunsaturated components thereby increasing theirboiling points, which facilitates subsequent separation of therespective components, as .by distillation.

The inventions disclosed and claimed in my ing the polyunsaturatedcomponents of the red.

oil and then separating them from the monounsaturated components.Application Ser. No. 681,765 discloses a method of manufacturing dimersby polymerizing the polyunsaturated components of fatty acids, such aslinseed oil or soybean oil fatty acids, from which saturated andmonounsaturated acids may then be removed if necessary or desirable. Thepresent application is a continuation-in-part of each of these earlierapplications.

' Each of these methods is characterized by the utilization of arelatively small amount of water maintained in solution in the fattyacids by application of pressure during a polymerization heat treatmentof intensity which would otherwise be destructive to the carboxylradicals of the fatty acids.

The chief problem in utilizing the methods of either of these inventionsis to carry them out on a commercial scale without concomitant equipmentof rodigious pro ortions and co t. The heating of large bodies of fattyacids to high temperatures with the use of ouantities of water whichestablish corresponding high pressures, and the holdin'r of the acids atsuch temperatures and pressures over prolonged periods of time, pose aproblem of providing practical equipment which will be of reasonableproportions as to size and cost in relation to throughput.

Expensive corrosion resistant alloys are requiredfor the fabrication ofpressure Vessels.

which permit the employment of temperatures and pressures of the orderinvolved without ruinous corrosion and forbidding safety hazards, But

' vessels fabricated from such alloys of a size ade- .of substantially1-5% water by weight.

quate to provide throughput which can be characterized in tons per day,rather than pounds per day, are enormously expensive, particularly iftheir utilization is limited to batch processing as distinguished fromcontinuous processing.

It is the object of this invention to provide apparatus for continuouslypolymerizing the polyunsaturated components of a mixture of fatty acidsand separating them as dimer acids from the less unsaturated componentswithout prohibitive equipment costs. It is also the objective to providea practical commercial process for effecting this dimerization andseparation which permits a throughput which is high in relation to theamount of equipment and to the cost of equipment utilized in theoperation.

This invention involves establishing a continuous flow of a stream ofmixed fatty acids from a stock storage tank to individual storage tanksin which the separated components are received at I the end of theprocess. The apparatus comprises means for pumping under the pressurerequisite at each stage of the operation and means for heating andcooling the stream at predetermined points in the cycle.

The fatty acids which are adapted to be used as raw materials, orstarting materials, in this process are mixed fatty acids which containpolyunsaturated components and less unsaturated components such as thefatty acids of linseed, soybean, cottonseed, corn and fish oils. Thefatty acids of all of these oils provide substantial yields ofpolymerized acids. On the other hand, red oil (commercial oleic acid) orthe fatty acids of tallow, lard oil or the like may be processed,although in such case, the primary purpose would probably be theenhancement of the value of the fatty acids themselves, rather than theproduction of the polymerized acids which would be recovered aslay-products. For convenience in describing this invention, all of thefatty acids which contain polyunsaturated components and lessunsaturated components will be termed the fatty acids of drying andsemi-drying oils to distinguish them from fatty acids such as commercialstearic which is substantially devoid of polyunsaturants.

The stream of mixed fatty acids is first conditioned for polymerizationby the introduction It is the function of the Water which is injectedinto the fatty acids to protect them against deterioration 01"decarboxylation which they otherwise would suffer under the temperaturesemployed in the operation. The amount of water, percent- 3 agewise, isnot precisely critical and, of course, willwary in accordance with thepermissible pressures for which the equipment is designed, the greaterthe percentage of water the greater the resultant pressure and viceversa. The apparatus components of the system, including the pumps, areadapted to operate at pressures which, at polymerizing temperatures,will pre vent vaporization of the water, so that the water remains inthe fatty acids and aiiords its full protective efiect.

Quantities of water substantially greater than 5% have not been found tobe desirable since they do not confer additional protective benefits andthey do increase the operating pressures which are required to hold themin liquid condition or in solution in the fatty acids. On the otherhand, substantially less than 1% by: weight of water based on the weightof the fatty acids may be insufiicient to accomplish the desiredinhibitory result. Best, operation is obtained by selecting a percentageof water within approximately the range indicated and then, adjustingthe water content of the fatty acids being treated to maintain the watercontent selected.

Preferably the fatty acids are dried under vacuum to such degree thattheir moisture content is of no significance from the point of view ofthe generation of steam pressure within the system, and then thepredetermined amount of water is added. The maintenance or" thepredetermined content of water in the flowing stream insures therequired stability of opera tional conditions and the continuation ofthe chosen relationships of temperature, pressure and duration oftreatment. for each quota of the stream. If the. stream of fatty acidswere not first dehydrated it might vary in moisture content. and thiswould unbalance. the operating conditions. Moisture contents above theexpected might even endanger the equipment itself as a result ofdevelopment of excessive pressure.

The Watered stream of fatty acids is next heated under pressure toeffect polymerization after which the pressure is released to flashdistill the monomers from the polymers. Considerations pertinent to therelationship. of the preferred method and. themost economical apparatusare several and interrelated. Although. polymerization commences slowlysomewhere in the neighborhood of 250 0., with most fatty acids, the rateof polymerization substantially doubles with each to C. temperaturerise. It follows that at substantially 400 C. the time required forpolymerization is but a fraction of that necessary at 250 C. Thus thesize of the equipment required to hold the body of fatty acids beingpolymerized for the time requisite decreases in inverse ratio to thetemperature utilized.

Since equipment suitable for holding the hot corrosive acids under highpressure must necessarily be stainless steel or the equivalent, andrelatively thick walled, it is desirable, to. mini:- mize its size. andhence its overall cost in order to reduce the fixed cost component ofeach unit.

of throughput. But, on the other hand, it is futile to attempt to reducethe fixed cost component by the use of high temperatures if the savingis nullified by the, added operating cost in.- herently involved in theutilization of the higher temperatures.

I solve this problem by heating the stream of fatty acids to apolymerizing temperature above that which is. requisite later to. flashdistill the.

stream, but chill it after polymerization to distillation temperature byheat exchange with the infeed, whereby the high temperature andconcomitant economical equipment are had at no operating cost greaterthan that represented by the radiation losses, which may be minimized byappropriate utilization of insulation.

Instead of utilizing the heat not required for distillation to preheatthe infeed, it may be utilized to generate the steam required for othersteps of the process, such as stripping steam or the operation of vacuumejector-s or even the high temperature steam for a counter-current fattyacid splitting tower. By this device, the stream or. fatty acids ispolymerized at optimum temperature and flash distilled at a lower, butalso optimum, temperature. By this method, I avoid flash distillationtemperatures which might tend to distill over the polymer with themonomer or which might tend to be destructive to the acid radicals afterthe release of pressure, which permits the moisture content tovolatilize.

While processing of the stock through the polymerizer and dash stillpreferably proceed as sequential steps to which the continuous stream ofstock is subjected, the polymerized component may also be recycledthrough the polymerizer, if desired, whereby the material passingthrough the polymerizing zone more than once becomesv more highlypolymerized than would otherwise be the case.

The apparatus of this invention is illustrated diagrammatically in theaccompanying flow sheet according to which the material to be processedis drawn from feed tank I by pump 2 which forcesit through heatexchangers 3 and 4 and drier 5. In heat exchanger heat is withdrawn fromthe dimerized acids which constitute the still residue, and in heatexchanger heat. iswithdrawn from the monomer acidvapors resulting fromdistillation. Drier 5 is utilized for the. purpose of insuring astandard moisture content for the stream of, material to be treated.

The material is fed from drier 5 to pump 5 which forces it under highpressure through the apparatus in which the polymerization isaccomplished. A pump 1, preferably a metering pump, forces a small butmeasured stream of water into the material discharged from pump 6 toprovide a. Water content of substantially l to 5%. After this thematerial enters heat exchanger .l in which it withdraws heat from thematerial which has been polymerized, but has not yet been distilled.

The material being processed then passes from the heat exchanger througha furnace iii in which it is heated to. a temperature approximating butnot equalling, the maximum temperature to be utilized in the process.From furnace It the fatty acids pass into autoclave H which is providedwith baiiies (not shown) which maintain the stream like character of theflow. The dimerization is completed in the autoclave and, since this is,an. exothermic reaction, the temperature of the fatty acids tends torise above the temperature to which they were. elevated in furnace Iii.From autoclave H the fatty acids may be conducted by line ba .1 to heatexchanger 9 Where they are cooled by the incoming feed directed tofurnace id. Preferably the amount of heat removed is sufiicient toreduce the temperature of the fatty acids to just that amount necessaryfor subsequent flash distillation. In order to control the temperatureof the fatty acids. to be subjected to the. flash distillation, heattransfer device 9 may be bypassed by line I2, so that the amount offatty acids subjected to the cooling action can be proportioned, inrelation to the/fatty acids fed directly to the flash still, by controlvalves It and I5. Thisarrangement provides flexibility adapting theequipment for the utilization of various fatty acid stocks and variouspolymerization temperatures.

From autoclave H and'exchanger 9, the fatty acids are delivered throughpressure control valve it which maintains pressure in the system betweenit and pump 5. This pressure must'at all times be suff cient to hold themoisture present in solution or in the liquid state (Whichever it is) toprotect the carboxylic radicals of the fatty acid from the decompositiontemperature tends to induce.

After passing throu h pressure control valve which the high it, thefatty acids are fed into fla h still if. The

monomer acids, that is, the unpolvmerized fatty acids, volatilize orvaporize rapidly, i. e., they flash. In other words, they vaporize to beultimately recovered as condensate and the hi her boiling point polymeror dimer acids are withdrawn as still residue. The flash still I! isoperated under a vacuum and steam is introduced into its lower portionby means of line I 8 to strip unpolymerized fattv acids from the stillresidue. This residue is withdrawn from the bottom of the still andconducted to heat exchange device 3 where it is cooled by the fatty acidinfeed, after which it is conducted to storage container I9.

The distillate is conducted from the hash still I! to the heat exchanger4 where it supplies heat to theincoming feed of fatty acids. The distillate then passes to condenser'zu from which it is'delivered to storae tank 2| The condenser is provided with cooling water b lines 22 and 23which are utilized to maintain the condenser at the desired operatingtemperature. An ejector or evacuator 24 is connected with condenser 2Hand is utilized to draw a vacuum on the condenser and the flash still.In accordance with accepted distillation practices, it is desirable tomaintain as reat a vacuum as possible in the flash still within thelimits of economical size of the evacuator or eductor. Under lessfavorable vacuum conditions it may be necessary to increase thetemperature of the stock in the flash still in order to effectvolatilization of some of the less volatile monomeric materials, but, inthis respect, it should. be remembered that the protective water is nolonger present in the stock and it is desirable therefore to hold thetemperature as low as possible in order to avoid deterioration ordecarboxylation of the products during dist llation.

The exact temperature and time conditions employed for effecting thepolymerization may be governed by the nature of the infeed stock, and ofcourse, the specifications of the equipment which is available. Ingeneral the time during which the fatty acids are subjected to thepolymerizing temperature will be governed by the nature of the fattyacid stock and the degree of polymerization which is desired, as well asby the actual polymerizing temperature. Thus, the polymerizing operationmay be completed to the extent desired in as little as approximately 20minutes, or the processing may be continued for as long as two hours ormore. Since the polymerization is conducted in a ba ed autoclave orelongated conduit, the time for polymerization may be controlledconveniently by adjustment of the rate of flow of material through thesystem.

By way of illustration, but not by way of limitation, polymerization mayproceed, for example, at a temperature of approximately 385 C. under apressure of 600 lbs. per square inch for a period of from 20 to 60minutes. There is also considerable latitude in the exact conditionsunder which flash distillation is conducted. For example, with apolymerizing temperature of 350 to 400 C., the dimer-monomer mixture maybe cooled to within the range of 260 to 360 C. before flash distilling.Preferably, but not necessarily, flash distillation may occur under anabsolute pressure of substantially 10 millimeters of mercury, and.monomer vapors ar stripped later from the residue by introducingsaturated steam at approximately (3., in the proportion of substantially1 1b. of steam to each 10 to 25} lbs. of residue,

While polymerization temperatures in excess of 400 C. have not beenmentioned specifically, itis to'be understood that temperatures up tothose'destructive to the fatty acids themselves may be employed providedthe water content of the fatty acids is increased proportionately toprovide proper protection against decarboxylation. However, 375 to 400C. would appear to constitute the operational range which is optimum atpresent in view of the limitations of presently available materials.

Obviously, precise operating conditions must bedetermined in relation tothe nature of the fatty acid stock beina treated and the end productsdesired. For instance, the temperature proper for flash distillationnecessarily varies with-the ratio of monomer to polymer after completionof polymerization. The greater the proportion of monomer the greatermust be the total available heat necessary to distill it,

The disclosure has been made primarily in relation to the processing offatty acids such as those obtained from soybean or cottonseed oil, i.e., acids in which the prevailing chain length is 18 carbon atoms. Foracids of greater chain length distillation temperatures should beproperly adjusted. Likewise, if the process be practiced to remove verysmall percentages of polyunsaturants from the acids so that the monomersare present in predominant proportions, then each distillationtemperature must be individually calculated. Since polymerization is anexothermic reaction, the increase in temperature due to it must be takeninto account in all calculations.

While it might be desirable in some cases to conform the specificationsof a given polymerization plant to the requirements of the processing ofa specific fatty acid stock, the apparatus of this invention has thevirtue of flexibility, that is, a sin' le piece of equipment may be usedto process many types of raw material by appropriate selection ofoperatin conditions. While waterin the fatty acids may be accomplishedat any time prior to their subjection to high heat, even beforeintroducinq them into the equipment, it is believed to be preferable toprovide in the equipment for the dehydration of the fatty acids underatmospheric or subatmospheric pressure, followed by watering. It is alsopreferable to provide the equipment with variable speed pumps and tohave the pressure control valve adjustable. These arrangements, togetherwith temperature control of the furnace and the adjustable by-pass ofthe heat exchanger J which is located between the autoclave and theflash still, provide a flexibility which permits one piece or equipmentto handle many types of raw material.

In any case, the size of the polymerization closure may be calculated toprovide the lowest equipment cost for each unit of throughput whichavailable construction materials permit,

without regard to operating costs. This is made possible by theutilization of polymerization temperatures above those requisite forflash distillation and the reuse of the excess heat, whereby utilizationof the low cost equipment entails no increased operating cost, save forradiation losses.

Having described my invention, I claim:

1. The method of removing polyunsaturated components as dimer acids froma mixture of fatty containing polyunsaturated fatty acids, said processcomprising establishing a flowing s ream of said mixed fatty acids,adding to said flowing stream substantially from one to five per centwater, heating said flowing stream to a temperature or" fromsubstantially 350 to 400 C., while maintaining a pressure sufficient toretain said Water in solution in the fatty acids to inhibitdecarboxylation of said fatty acids, holding said stream of fatty acidsat said polymerizing temperature for a period of substantially twentyminutes to an hour, cooling said stream of fatty acids to substantially260 to 360 0., releasing the pressure on said stream of fatty acids andflash distilling the unpolymerized components as distillate andrecovering the polymerized components as a residue.

2. The method or heat treating a mixture of fatty acids containingpolyunsaturants which comprises establishing a flowing stream of saidfatty acids, adding water to said stream in amount sufficient to inhibitdecarboxylation thereof during heating, and subjecting the fatty acidsin said stream to a temperature of substantially 350 to 400 C., under apressure of 300 6 to GOO-lbs. per square inch pressure, for a period oftime suiiicient to effect polymerization of polyunsaturated componentsin said stream, and then cooling the stream and flash distillingunpolymerized components from it.

3. The method of heat treating' a mixture of fatty acids containingpolyunsaturants which comprises establishing a flowing stream of saidfatty acids, adding water to said stream in amount sufficient to inhibitdecarboxylation thereof during heating, and subjecting the fatty acidsin said stream to a temperature of sub stantially 350 to 400 C., under apressure of 300 to 600 lbs. per. square inch pressure for a period oftime sufiicient to effect polymerization. of polyunsaturated componentsin said stream, and then cooling the stream and flash distillingunpolymerized components from it, at an absolute pressure notsubstantially exceeding 10 millimeters of mercury.

CHARLES G. GOEBEL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 414,936 Burcy Nov. 12, 1889 1,474,772 Foster 1; Nov. 20, 19231,594,024 Soule July 27, 1926 1,828,691 Stransky et a1. Oct. 26, 19311,856,021 Bentel Apr. 26, 1932 2,006,186 Stines June 25, 1935 2,109,347Beekhuis Feb. 22, 1935 2,054,096 Potts et a1. Sept. 15, 1936 2,086,808Kallam July 13, 1937 2,152,665 Rosenthal Apr. 4, 1939 2,224,984 Potts eta1 Dec. 17, 1940 2,260,111 Caldwell Oct. 21, 1941 2,310,986 Murphy Feb.16, 1943 2,435,745 Ittner Feb. 10, 1948 2,482,761 Goebel Sept. 27, 19492,489,713 Leaders Nov, 29, 1949 2,495,071 Mills Jan. 17, 1950

1. THE METHOD OF REMOVING POLYUNSATURATED COMPONENTS AS DIMR ACIDS FROMA MIXTURE OF FATTY ACIDS CONTAINING OLYUNSATURATED FATTY ACIDS, SAIDPROCESS COMPRISING ESTABLISHING A FLOWING STREAM OF SAID MIXED FATTYACIDS, ADDING TO SAID FLOWING STREAM SUBSTANTIALLY FROM ONE TO FIVE PERCENT WATER; HEATING SAID FLOWING STREAM TO A TEMPERATURE OF FROMSUBSTANTIALLY 350* TO 400* C., WHILE MAINTAINING A PRESSURE SUFFICIENTTO RETAIN SAID WATER IN SOLUTION IN THE FATTY ACIDS TO INHIBITDECARBOXYLATION OF SAID FATTY ACIDS, HOLDING SAID STREAM OF FATTY ACIDSAT SAID POLYMERIZING TEMPERATURE FOR A PERIOD OF SUBSTANTIALLY TWENTYMINUTES TO AN HOUR, COOLING SAID STREAM OF FATTY ACIDS TO SUBSTANTIALLY260* TO 360* C., RELEASING THE PRESSURE ON SAID STREAM OF FATTY ACIDSAND FLASH DISTILLING THE UNPOLYMERIZED COMPONENTS AS DISTILLATE ANDRECOVERING THE POLYMERIZED COMPONENTS AS A RESIDUE.